Reliability of the lateral abdominal muscle thickness measurements in idiopathic scoliosis patients.

BACKGROUND: To date, the reliability of ultrasound imaging (US) measures of the abdominal muscle thickness in idiopathic scoliosis (IS) patients during early stages of adolescence has not been confirmed.

OBJECTIVE: To assess the intra-rater reliability of US measures of the thickness of the external oblique (EO), internal oblique (IO), and transversus abdominis (TrA) on convex and concave body sides in adolescents with IS.

DESIGN: One-way repeated-measures analysis of variance (ANOVA) and reliability study.

METHODS: Fifteen patients diagnosed IS were included between the ages of 9 and 14 years. Three repeated US measurements were recorded in the supine resting position over 2 sessions, 24 h apart.

RESULTS: By assessing the mean value from the first two measurements (ICC3,2 ), the reliability was between .76 and .95 for all examined muscles on the convex and concave sides. The reliability for the mean values from three measurements (ICC3,3 ) was between .81 and .96. The smallest detectable difference values for single measurements were twice as high on the convex side than on the concave side for all examined abdominal muscles.

CONCLUSION: US measurements of the thickness of the EO, IO, and TrA muscles in supine rest position in adolescent IS patients are reliable. In order to increase measurement reliability, and due to variability in reliability between concave and convex body side, we recommend using the mean of three consecutive measurements of the EO, IO, and TrA muscles for adolescents with IS.